1. Field of the Invention
The present invention relates to a recorder, and more particularly to a serial recorder which uses a stepping motor as a drive source to move at least a recording head for scan.
2. Related Background Art
In a prior art serial recorder, a hybrid or permanent magnet (PM) type stepping motor or a brushless motor is frequently used as a motor for driving a carriage which carries a recording head for scan.
For example, the brushless motor usually uses a Hall element to detect a position of a magnetic pole of a rotor for controlling energization, and uses an optical or magnetic encoder to detect a velocity of the rotor.
Such a brushless motor, however, has the following problems.
(1) Positioning between stator magnetic poles and Hall elements is required.
(2) Where the energization is switched by the Hall elements, the positions of the Hall elements and the stator are uniquely defined and an energization method for the motor is fixed. For example, for a 180.degree. energization control and a 90.degree. energization control, the positions of the Hall elements relative to the stator magnetic poles differ by 45.degree. electrically from each other. Accordingly, in order to effect two different energization controls to one motor, it is necessary to double the number of Hall elements and arrange them at appropriate positions for the energization control.
Japanese Patent Applications Laid-Open Nos. 62-193548 and 62-193549 disclose stepping motors which use an encoder output to control the energization. They merely disclose structures of motors having encoders arranged at predetermined positions but do not disclose a motor drive control circuit nor a method therefor.
A prior filed U.S. application Ser. No. 401,483, filed Aug. 30, 1989, which is a continuation of U.S. application Ser. No. 259,259, filed Oct. 18, 1988, and assigned to the assignee of the subject application, discloses a controller for a stepping motor, in which an encoder having marks which are equal in number to an integer multiple of the number of magnetic poles of a rotor is fixed to a shaft of the rotor, and the number of marks of the encoder is counted at a predetermined position on a stator as the rotor is rotated and the energization to the coils of the stator is switched when the count reaches a predetermined value. In the past, the drive control for the stepping motor has been effected by open-loop controlling the number of drive pulses for the motor and a pulse frequency in a simple manner. However, when a 5 stepping motor is used as the carriage drive motor and it is driven by an open loop control, an offensive noise "queen" due to vibration of a rotor of the stepping motor is generated. When the carriage is moved, stopped or reversed, that is, when the stepping motor is started, stopped or reversed, a large noise "bang" is generated because the stepping motor is started or stopped with vibration. Those noises are problem in a relatively noise-free printer such as bubble jet printer or ink jet printer.
The brushless motor may be used as the carriage drive motor. However, the brushless motor has a long rise time at the start-up and hence it is not appropriate as a carriage drive motor which repeats, starts, stops and reverses for each line. High speed recording is not attained with such brushless motor.